Apparatus for sterilizing packaged material

ABSTRACT

THE STRIP OF PACKAGING MATERIAL IS LED THROUGH THE LIQIUD STERILIZATION CHAMBER IN A LOOPED PATH SO AS TO EXPOSE THE STRIP FOR AN EXTNEDED PERIOD OF TIME. THE EXIT END OF THE LOOPED PATH COMMUNICATES IN SEALED RELATION WITH AN ENCLOSED CHAMBER WHICH IS MAINTAINED IN A STERILE ATMOSPHERE. AN EXTENDED STERILIZING PATH IS THUS PROVIDED TO KILL GERMS THAT MAY OTHERWISE EXIST ON THE PACKAGING STRIP.

Sept. 19, 1972 w, LOLIGER EI'AL 3,692,468

APPARATUS FOR STERILIZING PACKAGED MATERIAL Filed July 21, 1970 2 Sheets-Sheet l 30, 2a 2 f f Inventors;

WlL.l LOLIGEQ RUOOLF' Sc HMIED A ATTOR S Sept. 19, 1972 w LOLIGER ETAL APPARATUS FOR STERILIZING PACKAGED MATERIAL Filed July 21, 1970 2 Sheets-Sheet 2 n I C Q l; LL La w m United States Patent G "ice" US. CI. 21-58 12 Claims ABSTRACT OF THE DISCLOSURE The strip of packaging material is led through the liquid sterilization chamber in a looped path so as to expose the strip for an extended period of time. The exit end of the looped path communicates in sealed relation with an enclosed chamber which is maintained in a sterile atmosphere. An extended sterilizing path is thus provided to kill germs that may otherwise exist on the packaging strip.

This invention relates to an apparatus for sterilizing packaging material and more particularly, strip packaging material conducted through sterilizing baths.

It has been known that strip-like packaging material, for example, paper coated at one side with a synthetic substance can be conducted through a bath containing a sterilizing liquid, such as a hydrogen peroxide solution having a 20% concentration of H Further, it has been known that when the bath temperature is raised to 60 C. for example, a 6-second stay of a portion of the strip in this bath kills even heat-resisting germs. Naturally, care must be taken to ensure that the side of the strip coming into subsequent contact with the sterile goods to be packaged does not become reinfected.

However, in practice, it has been found that in spite of a sufiicient time of immersion of the portion of strip in the liquid sterilizing bath, the strip emerging from the bath has frequently carried germs that have not been killed. This phenomenon is naturally an extremely detrimental one. If, for example, the strip emerging from the liquid bath is conducted directly into an aseptic packaging machine and is there filled with sterile goods, e.g., degerminated milk, then such still-living germs would not be immediately detectable. Further, these germs may even infect the packages, or even the aseptic machine, so that under certain conditions, the production of many hours of operation of the machine subsequently becomes spoiled.

In accordance with the invention it has been recognized that a reinfection can occur in the region where a strip emerges from the liquid bath because of living germs that were carried into the bath or that were deposited on the surface of the strip from the surrounding air. For example, the germs might become transported into the surface zone of the bath and thereafter conducted along the shortest path to the region where the strip emerges from the bath so that the germs can be carried along on the surface of the strip as the strip emerges. Under certain conditions, the stay of these germs in the bath is shorter than the time required for the bath to positively kill them. This, of course, makes aseptic operation impossible.

Accordingly, it is an object of the invention to create an aseptic path for the sterilization of a packaging strip sufiicient to eliminate destructive germs.

It is another object of the invention to prolong the duration of a packaging strip within a sterilizing bath within a minimum of space.

It is another object of the invention to provide an aseptic passage for conducting a sterilized packaging strip from a sterilizing bath to a packaging machine.

3,692,468 Patented Sept. 19, 1972 Briefly, the invention provides an apparatus for sterilizing a packaging strip wherein the place where the strip is passed into a liquid sterilizing bath within a tank and the place where the strip emerges from the liquid are separated from one another by a separating wall which dips into the liquid. The depth to which the separating wall dips into the liquid is dimensioned so that a germ getting on the strip at the place where the strip enters the liquid is positively killed, or is at least weakened enough to be definitely killed by a following application of heat, before such a germ can arrive at the place where the strip emerges from the liquid as a result of the movement of the liquid and be deposited thereon. In addition, the region above the surface level of the liquid at the place where the strip emerges is maintained as a sterile atmosphere.

The separating wall ensures that any germ arriving at the surface level of the liquid along with the strip is subjected to a sufliciently long stay in the liquid sterilizing bath to be killed or weakened for subsequent killing in a following heating of the strip, for example, for the purpose of drying the strip.

In one embodiment, the separating wall is made tubular so that the strip is passed through the tube before emerging from the bath. In such a case, a means such as a deviating roller is used to loop the strip in the bath to allow the strip to move upwardly through the tube. In another embodiment, the separating wall may serve directly as a carrier of a deviating roller for the strip below the surface level.

Also, the tank and the separating wall can be constructed so as to be movable relative to one another for a temporary emergence of the strip from the liquid. It is moreover desirable to dispose a means for heating the liquid in the tank.

In addition, the apparatus communicates the emerging side of the tank directly with the chamber which is maintained under aseptic conditions for passage of the packaging strip directly to a packaging machine. This chamber is maintained in an aseptic state by any suitable means such as a blower arrangement which directs hot filtered and sterilized air into the chamber. This arrangement can also be used so that the hot air is used to heat the longitudinal edges of the strip to facilitate bonding, as by overlapping, of the edges together.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 schematically illustrates an apparatus according to the invention, assembled with an aseptic packaging machine;

FIG. 2 illustrates partly in elevation and partly in section a view taken along line II-II of the tank for the sterilizing liquid of FIG. 1;

FIG. 3 illustrates a view taken on line IIIIII of FIG. 1;

FIG. 4 illustrates a cross sectional view corresponding to that of FIG. 3 of a modified separating wall according to the invention; and

FIG. 5 illustrates a portion of an arrangement according to FIG. 1 with a separating wall according to FIG. 4.

Referring to FIG. 1, the sterilizing apparatus 14 which is supplied with a strip 12 of packaging material from a supply roll 11 over a deviating roll 13 includes a tank 15, which is filled up to a surface level 16 with liquid having a sterilizing property, for example, with a 20% solution of hydrogen peroxide (H 0 to form a sterilizing bath. In addition, an electric heating unit 10 is mounted in the lower part of the tank in order to maintain the liquid bath, for example, at a temperature of 60 C. The apparatus 14 further has a separating wall 17 which is made in tubular form e.g. of a rectangular profile as shown in FIG. 3, and which is immersed in the bath. The separating wall 17 carries holders "18 at the lower end in which a deviating roller 19 is mounted for rotation. The separating wall 17 is, by means of a flange-connection 20, connected hermetically with a housing 21 which encloses a sterile chamber 22 of an aseptic packaging machine 23. In use, after being conducted over the first deviating roller 13, the strip 12 is passed into the bath and passed about the second deviating roller 19 into the space enclosed by the tubular separating wall 17. Thereafter, the strip 12 emerges into the chamber 22 and passes between a pair of squeezing rollers 24 which free the strip of excess liquid. The strip 12 then runs over a roller 25 and passes downwardly. During downward travel through the chamber 22, the strip 12 becomes formed into a tube 26 as is known by overlapping and bonding of the side edges together along a directrix.

The packaging machine 23 includes a filling tube 27 which injects the goods being packaged into the formed tube 26. In the present case, a sterile liquid, for example,

degerminated milk is supplied through the filling tube 27.

The housing 21 is set on the base 28 of the machine over a shaping and bonding mechanism 29 located in the base 28. This mechanism 29 has bonding shoes 31 which circulate upon belts 30, and which during movement in opposition to the tube 26, press into the tube wall transversely of its longitudinal axis to make a transverse bond ing-seam 32. A similar mechanism operates perpendicularly to the plane of the drawing, so that by the aid of transverse seams set alternately in the plane of the drawing and perpendicularly thereto, the familiar tetrahedronshaped packages 33 are produced. These packages 33 can be separated from one another by a cut in the region of the bonding seam.

During packaging, the liquid being packaged forms a surface level 34 in the tube. In this way, all the packages are ensured of being completely filled with liquid.

The chamber 22 is provided with a suitable heating means so as to maintain the chamber interior in an aseptic state. For example, for an initial sterilization of the chamber 22, hot air is introduced by a blower 35 which draws air in from the surroundings to flow across an electric heater 36 which heats the air to a temperature of, for example, 200" C. The hot air is then conducted through a sterile filter '37, and is finally made to flow through a distributor 38 into the interior of the chamber. This emerging hot air serves at the same time for heating the longitudinal edges of the strip that are to be bonded and overlapped by pressure-shoes 3-9. For the purpose of positively maintaining aseptic conditions after completion of this initial sterilization of the chamber interior, it is sufficient under certain conditions to maintain a sterile atmosphere with the heat shut off or reduced by the aid of the blower 35 and sterile filter 37. However, a separate heating device would have to be provided for bonding the longitudinal edges of the strip 12.

In operating, the strip 12 is pulled off the supply roll, for example, at a speed of 30 cm. per second. The distance of the roller 19 from the surface level 16 is chosen so that at this strip speed, a portion of the strip remains approximately 7 seconds in the liquid bath, between its immersion into the liquid and its emergence out of the liquid. This length of time is sufiicient to positively kill even heat-resisting germs. In the present case, the length of the path between the surface level 16 and the roller 19 amounts to 1 meter. The separating wall 17 therefore dips about 65 cm. into the liquid. For a germ that has come loose from the strip surface to be able to move from the liquid surface where the strip enters to the liquid surface where the strip emerges the germ would have to cover a path of at least 1.3 meters, corresponding to a time of at least 4 seconds. However, because germs never take the theoretical shortest path through the bath, it is sure they will stay in the bath for more than 7 seconds.

The tank 15 is further mounted in a displaceable guided manner between pairs of rollers 40, 41 so as to be moved downward out of the operative position as shown. To this end, rollers 42 are mounted below the rollers 40, 41 to guide the tank 15 in the lower position. The lowering allows the strip to be brought out of the liquid during a temporary stoppage of the machine. Also, during an initial introduction of the strip into the machine, the strip can be laid round the deviating rollers for easier introduction into the interior of the separating wall 17 Further, since chemically-acting sterilization liquids, for example, the hydrogen peroxide mentioned above, may deterimentally affect the strip during a lengthy standstill of the strip in the liquid bath and in particular the metal foil attached thereto, the provision for withdrawing the tank 15 allows this eifect to be avoided.

The depth to which the separating wall 17 is immersed depends essentially on the speed of the strip, on the bath temperature, and on the concentration of the chemicallyacting sterilization liquid. With high temperatures and strong concentrations the depth of immersion can be lessened.

It is not necessary that the separating wall form a closed tube. For example, referring to FIG. 4, a tank 51, of rectangular profile, is subdivided by a central wall 52 into the two chambers 53 and 54. The strip 55 is, for example, introduced into the bath in chamber 53 and passes out of chamber 54. The chamber '54 as shown in FIG. 5, is connected to the chamber 22 which is filled with the sterile atmosphere so that no germ for surrounding air can enter.

It is noted that the invention is not limited to the illustrated examples of construction but may also be applied to the so-called mixed sterilization processes. These are characterized in that a chemically-acting sterilization is supplemented by a heat-sterilization, such as is indicated by way of example in FIG. 1. As shown by dot-dash lines, heating plates 61, '62 are disposed at both sides of the strip 12 between the pair of squeezing rollers 24 and the rotating roller 25 in order to heat both sides of the strip by radiation. Such a mixed sterilization is characterized in that a sterilization machine by itself, may not be sufiicient to kill the germs. With the illustrated example, it would suffice if the chemically-acting liquid only weakened germs to such an extent that the second means employed, namely heating by the aid of the plates 61 and 62, finally effected the killing.

Such mixed sterilization processes have the advantage that they can be made with smaller dimensions than those designed to kill germs by a single sterilization process. For example, it would be possible to use a less concen trated chemically-acting sterilization liquid. There would then be, for example, a less sharp attack of the sterilization liquid on the strip material. Further, since the time that the strip stays in the sterilizing liquid can be made substantially shorter in the case of a following heat-sterilization, the path of the strip in the liquid bath for a given strip speed can be shortened thus making the ar rangement simpler.

We claim:

1. An apparatus for sterilizing packaging material of strip form comprising a tank having a sterilizing liquid therein,

a separating wall dipped into said liquid within said tank to divide said tank into at least two sequentially connected chambers, the surface of liquid in one chamber being sealed from the surface of liquid in the other chamber, said strip being guided from a zone of immersion in said one chamber around the deepest point of penetration of said wall to a zone of emersion in said other of said chambers, said point of penetration being located such that a germ arriving in the liquid in said zone of immersion has to travel a distance within the liquid so as to be destroyed before reaching said zone of emersion as a result of motion within the liquid, and

means in communication with said other chamber for creating a sterile atmosphere outside said other chamber.

2. An apparatus as set forth in claim 1 wherein said tank and said wall are movably mounted with respect to each other for a temporary removal of said wall from said liquid.

3. An apparatus as set forth in claim 1 which further comprises means for heating said liquid in said tank.

4. An apparatus as set forth in claim 1 which further comprises means for directing the strips sequentially through said chambers.

5. An apparatus as set forth in claim 1 further comprising heating means downstream of said other chamber for heating the strip.

6'. An apparatus as set forth in claim 1 wherein said wall is tubular with said other chamber being formed longitudinally therein.

7. An apparatus as set forth in claim 6 which further comprises a deviating roller in said tank for directing the strip into the interior of said tubular wall.

8. An apparatus as set forth in claim 7 wherein said roller is supported from said wall.

9. A method of sterilizing packaging material of strip form comprising the steps of positioning a separating wall in a tank of sterilizing liquid to divide the tank into at least two sequentially connected chambers with the surface of liquid in one chamber being sealed from the surface of liquid in the other chamber; and

guiding a strip of packaging material through a zone of immersion in said one chamber around the deepest point of penetration of the separating wall to a zone of emersion in said other chamber, said deepest point of penetration being spaced from said surfaces of liquid a distance sufficient to permit destruction of a germ arriving in said zone of immersion before arrival of said germ in said zone of emersion through the liquid in said chambers while preventing reinfection of said strip in said zone of emersion, said distance being determined by the speed of said strip, the temperature of said liquid and the concentration of said liquid.

10. A method as set forth in claim 9 wherein said strip is emersed in said liquid for 7 seconds and said distance is 65 centimeters.

11. A method of sterilizing packaging material of strip form comprising the steps of positioning a separating wall in a tank of sterilizing liquid to divide the tank into at least two sequentially connected chambers with the surface of liquid in one chamber being sealed from the surface of liquid in the other chamber;

guiding a strip of packaging material through a zone of immersion in said one chamber around the deepest point of penetration of the separating wall to a zone of emersion in said other chamber, said deepest point of penetration being spaced from said surfaces of liquid a distance sufficient to permit sufficient weakening of a germ arriving in said zone of immersion before arrival of said germ in said zone of emersion through the liquid in said chambers while preventing reinfection of said strip in said zone of emersion, said distance being determined by the speed of said strip, the temperature of said liquid and the concentration of said liquid; and

subsequently heating said strip after emerging from said zone of emersion in said other chamber to complete the destruction of said germ, wherein said distance is further determined by the amount of heat imparted to said strip in said subsequent step of heating.

12. An apparatus for sterilizing packaging material of strip form comprising a tank having a sterilizing liquid therein,

a separating wall dipped into said liquid within said tank to divide said tank into at least two sequentially connected chambers, the surface of liquid in one chamber being sealed from the surface of liquid in the other chamber, said strip being guided from a zone of immersion in said one chamber around the deepest point of penetration of said wall to a zone of emersion in said other of said chambers, said point of penetration being located such that a germ arriving in the liquid in said zone of immersion has to travel a distance within the liquid so as to be sufficiently weakened before reaching said zone of emersion as a result of motion within the liquid,

means in communication with said other chamber for creating a sterile atmosphere outside said other chamber, and

heating means Within said means for heating said strip to complete the destruction of said germ.

References Cited UNITED STATES PATENTS 3,511,592 5/1970 Tuma 21-92 3,466,841 9/1969 Rausing 2191 X 3,466,850 9/1969 Hudson 2192 UX 3,440,003 4/1969 Tuma 21--92 X 3,383,831 5/1968 Goldsmith et al 21-92 X MORRIS O. WOLK, Primary Examiner D. G. MILLMAN, Assistant Examiner US. Cl. X.R. 2191, 92 

